From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH RFC] VT-d: honor firmware-first mode in XSA-59 workaround code Date: Wed, 21 May 2014 17:33:56 +0100 Message-ID: <537CD574.3030701@citrix.com> References: <537CEBD20200007800014A29@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1Wn9Sz-0000eg-MY for xen-devel@lists.xenproject.org; Wed, 21 May 2014 16:34:09 +0000 In-Reply-To: <537CEBD20200007800014A29@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: Yang Z Zhang , xen-devel , Malcolm Crossley , Kevin Tian , Donald D Dugger List-Id: xen-devel@lists.xenproject.org On 21/05/14 17:09, Jan Beulich wrote: > When firmware-first mode is being indicated by firmware, we shouldn't > be modifying AER registers - these ar considered to be owned by "these are" > firmware in that case. Violating this is being reported to result in > SMI (or was it SCI?) storms. SMM livelock. The exact problem was a 2.6.32 kernel ignoring firmware-first and disabling reporting on the root ports but not endpoint devices, causing the SMM handler to fail to find the issue, and fail to clear the SMI. However, as part of the investigation, we identified that Xen was also violating firmware-first as part of XSA-59 ~Andrew > While circumventing the workaround means > re-exposing affected hosts to the XSA-59 issues, this in any event > seems better than not booting at all. Respective messages are being > issued to the log, so the situation can be diagnosed. > > The basic building blocks were taken from Linux 3.15-rc. > > Reported-by: Andrew Cooper > Reported-by: Malcolm Crossley > Signed-off-by: Jan Beulich